Were Kerry to agree to either job – and secretary of state clearly is more in line with his professional background, and would be the more poetic end-cap to his lifestory as the son of a diplomat and the chairman of the Senate Foreign Relations Committee—it would trigger a special election in Massachusetts to fill his Senate seat.

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At that point, Governor Deval Patrick would become a major player in the state and national political calculus.

The question confronting Patrick is whether he would replicate his decision of 2009, when he and his fellow Democrats changed the state’s Senate succession law so that the governor can immediately fill a Senate vacancy while a special election campaign is held to fill it permanently.

Previously, the governor alone filled the job until the next regularly scheduled election.

After Senator Edward M. Kennedy died, Patrick vowed not to give the temporary appointment to anyone who would be a candidate in the special election. To do so, he suggested, would give that candidate an unfair advantage on the rest of the field.

The governor ended up tapping longtime Kennedy aide Paul G. Kirk Jr. to fill the post while Democrat Martha Coakley and Republican Scott Brown battled it out in the special election.

It’s how that campaign ended, though, that may prompt a change in decision-making were there to be a need for a special election to fill Kerry’s seat.

Brown beat Coakley in the 2010 special election, stunning the Democrats and bolstering GOP opposition to Obama’s first-term agenda.

Her candidacy cleared the field of a group that ranged from liberal activist Alan Khazei to Newton Mayor Setti Warren.

Were Kerry to join the administration, Patrick could boost his national party, as well as the prospects for the president’s second-term agenda, by giving the temporary Senate appointment to the Democrat who would also be the party’s choice to run in the special election.

Not only would that avoid a damaging and expensive Democratic primary against what would surely be a united Republican front behind Brown, but it also would give the Democratic candidate a platform from which to audition for the job permanently, and to fund-raise for his or her special election campaign.

The challenge for Patrick would be squaring his lofty language about fairness from 2009 with a more partisan decision three years later.

One potential out? Bolstering the president’s agenda.

The Democrats ended up expanding their Senate majority over the Republicans last week from their current 53-47 to a 55-45 balance expected when the new Congress is sworn in on Jan. 3, 2013. They could afford to lose Kerry’s seat to a Republican like Brown and not give up their majority control of the chamber.

But presuming Kerry joined the Cabinet around January’s presidential inauguration, and Warren were elevated just weeks after taking office from junior senator to senior senator, a Brown win in the special election would create a situation where the two Bay State colleagues would most likely cancel out each other’s votes on critical issues expected in a second Obama term.

They include any tweaks to Obamacare, any changes to the tax code, and any votes on women’s issues, whether they be related to abortion rights or new justices to the Supreme Court who might decide on any challenge to Roe v. Wade.

It was a warning that Brown would vote against the interests of Massachusetts women on those latter issues in particular that proved to be most effective for Warren in her just-completed campaign.

Given the specter of such a political stalemate, Patrick may be pressured – or feel self-imposed pressure – to do all he can to boost the chances of a Democrat winning a special election to replace Kerry.

He may, for example, seek temporary replacement in the template of an Elizabeth Warren – say an Attorney General Martha Coakley, or a US Attorney Carmen Ortiz – and release any such choice from his 2009 precondition that they not run in the special election.

It would force Patrick to explain any such reversal, but the political fallout for him would be minimal: He has already said he is not seeking a third term.

And it could also boost his pal, the president, who invited him to the White House for dinner last Friday night.